Substitute circuit for a plurality of functional units

ABSTRACT

For a defective functional unit (FE1), it is possible to switch over via electronic input and output changeover switches (EUS1, AUS1) via a combination unit (KOM) to a substitute functional unit (EFE). The input signal (ES1) is supplied via a combiner (VK1) to the substitute functional unit (EFE) and is supplied via a splitter (VK2) to the output changeover switches (AUS1, . . . ), and is connected through only by the output changeover switch (AUS1) of the defective functional unit (FE1).

BACKGROUND OF THE INVENTION

The invention relates to a substitute circuit for a plurality offunctional units.

A substitute circuit which is connected via mechanical switches ispresented in the Patent Abstract of Patent JP-A-59 011 454.

It is known for substitute circuits to be provided in order to improvethe operational reliability. If a functional unit, for example anassembly, fails, this functional unit is isolated from the signal path(or the signal paths), and a substitute functional unit is connected inits stead. Relays have been used for changing over; in the case ofdigital signals, an implementation of the switching over is alsopossible by means of logic modules.

Laid-Open Specification of German reference DE 41 32 598 A1 discloses asystem for switching over telecommunications devices, in which achangeover to a substitute device is made for the purpose ofsubstitution or for testing one of these devices. Relays are used forswitching over.

The use of relays for switching over operational functional units andsubstitute functional units is extremely problematic. The reliability ofthe relays decreases rapidly for the changeover operations, which arecarried out extremely rarely.

In the case of a substitute circuit which processes digital or analogsignals at relatively high frequencies of about 30 Megahertz (MHz) oreven several Gigahertz, further problems arise.

The relay contacts have excessive capacitances, so that their use is notfeasible for this reason alone. In addition, this solution wouldnecessitate the provision of greater power.

The generally used ECL (emitter couple logic) technology requiresconsiderable power levels, so that logic circuits are not ideal forchanging over, just for reasons of power consumption. In addition, thereare also no modules with which implementation would be feasible forhigher frequencies.

Diode switches which are more suitable for changeover purposes in theradio-frequency range are known from the German Examined Specification26 08 117.

The Laid-Open Specification of German reference DE 41 02 930 A1discloses a circuit for splitting or combining radio-frequency power, inwhich the initial outlet impedance, which acts between the individualpores in each case, is formed by an absorber resistor, which isconnected to ground at one end, for splitting radio-frequency power,which is supplied from a sum port, to a plurality of individual portsand for combining radio-frequency power, which is supplied fromindividual ports, in a sum port. However, only a low level of decouplingis provided between the inputs and the outputs in this arrangement.

Combiners for VHF and UHF signals are described in the journal"MICROWAVES and RF", December 1990, pages 100 to 108 and October 1993,pages 81 to 86 and 132. There is no reference quoted for use withdigital signals or for substitute circuits.

SUMMARY OF THE INVENTION

The object of the invention is to specify a substitute circuit, which issuitable for higher frequencies, for a plurality of functional units.

The use of in each case only one substitute functional unit for aplurality of operational functional units is particularly advantageous.Duplication of systems or functional units is generally no longernecessary for a high level of fail-safety.

The use of double distributors/combiners which are constructed usingtransformers has been found to be particularly expedient. The doubledistributors/combiners are used for distributing a signal from an inputbetween two outputs or for combining two signals onto this output. Thesepassive components require no operating power whatsoever and have inputsand outputs which are decoupled excellently.

Combiners and distributors can be designed using pin-diodes, as aparticularly simple, cost-effective and advantageous variant.

A plurality of substitute functional units can also be provided forfurther increased reliability, and are each connected to the associatedsubstitute functional units via a separate combination circuit.

Pin-diode combinations are provided as electronic changeover switches.The attenuation of the switches becomes optimal by pin-diodes which areconnected to ground.

It is expedient to accommodate the pin-diode changeover switches on theassemblies of the functional units.

Each functional unit (assembly) expediently contains a so-calledrack-mounted computer for monitoring, control and signaling. Its dataand the data of other functional units are supplied to a logic circuit,which is expediently located on the combination assembly, disconnectsthe defective functional units in the event of a fault, and inserts thesubstitute functional unit.

The use of a plurality of substitute functional units is, of course,also possible in order further to increase the reliability.

BRIEF DESCRIPTION OF THE DRAWINGS

The features of the present invention which are believed to be novel,are set forth with particularity in the appended claims. The invention,together with further objects and advantages, may best be understood byreference to the following description taken in conjunction with theaccompanying drawings, in the several Figures of which like referencenumerals identify like elements, and in which:

FIG. 1 shows a block diagram of the invention,

FIG. 2 shows a substitute circuit having a plurality of substitutefunctional units,

FIG. 3 shows an exemplary embodiment of a distributor/combiner,

FIG. 4 shows an advantageous drive for a pin-diode changeover switch,

FIG. 5 shows a further drive option for a pin-diode changeover switch,and FIG. 6 shows an outline circuit diagram of a combiner,

FIG. 7 shows an outline circuit diagram of a distributor,

FIG. 8 shows an exemplary embodiment of a combiner, and

FIG. 9 shows an exemplary embodiment of a distributor.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

FIG. 1 shows the principle of the substitute circuit according to theinvention. One substitute functional unit EFE is assigned to a pluralityof identical functional units FE1, FE2, . . . The outline circuitdiagram assumes that there is in each case only one digital input signalES1, ES2 . . . and one output signal AS1, AS2 . . . per functional unit.Each functional unit is supplied with its input signal ES1, ES2, . . .via a signal input SE1, SE2, . . . of an input changeover switch EUS1,EUS2, . . . , while the output signal AS1, AS2, . . . is emitted via anoutput changeover switch AUS1, AUS2, . . . at a signal output SA1, SA2,. . . If a plurality of input signals are supplied to one functionalunit and/or if a plurality of output signals are emitted, then thesesignals are supplied via further changeover switches.

The second output of each input changeover switch EUS1, EUS2, . . . isin each case routed to an input E1, E2, . . . of a combination unit KOM.Outputs A1, A2, . . . of the combination unit are routed in acorresponding manner to second inputs of the output changeover switchesAUS1, AUS2, . . . The functional units are connected via data linesDL--in this case a bus system--to a control logic device STL which isarranged on the combination unit KOM.

A passive combiner VK1, which is constructed from double 10distributors/combiners ZVK, is illustrated on the combination unit KOM.In each case one of eight possible input signals is connected through toa first amplifier V1 which passes on this signal, amplified to theoriginal input level and as a substitute input signal EES, to asubstitute functional unit EFE. The substitute output signal EAS issplit via a second amplifier V2 and a passive combiner VK2 between (inthis case) eight outputs, and is supplied in each case to a second inputof an output changeover switch AUS1, AUS2, . . . The substitutefunctional unit EFE is also connected via further data lines DLE to thelogic circuit LS. The operation of the substitute functional unit canalso be monitored via these data lines.

The electronic changeover switches are configured as pin-diodechangeover switches and have two diodes D1 and D2, which areinterconnected by their same connections.

In the case of the input changeover switches, a further diode D11 or D12is in each case provided at least at one of their outputs, which diodeis forward biased in order to increase the attenuation when the secondswitch output is not active. The same changeover switches are used forthe output changeover switches.

If, for example, the monitoring of the first functional unit FE1 detectsa defect, then this is reported to the control logic device STL via thedata lines DL. The control logic device STL connects the first inputsignal ES1 through via control lines LS to the second output of thefirst input changeover switch EUS1, and thus to the first input E1 ofthe combination unit KOM. No signal is present at any of the otherinputs E2 to E8 of the first distributor/combiner VK1. The input signalES1 passes to the amplifier V1, is amplified there to the originallevel, and is supplied as a substitute input signal EES to thesubstitute functional unit EFE. The latter produces a correspondingsubstitute output signal EAS, whose level is initially increased by thesecond amplifier V2, and then emits this at the normal level to all theoutputs A1 to A8 of the second distributor/combiner VK2.

Only the first output changeover switch AUS1 connects the substituteoutput signal EAS through to its signal output SA1, however.

The logic circuit also signals which functional unit has failed. Thedefective functional unit FE1 can be removed and can be replaced by anintact functional unit. FIG. 2 shows a block diagram having twocombination units KOM1 and KOM2, as well as two substitute functionalunits EFE1 and EFE2. Input changeover switches EUS31 and EUS32 are used,each having three outputs, one of which in each case is connected to thefunctional unit FE1 or FE2, respectively, and the others are connectedto in each case one combination device KOM1 or KOM2. Correspondinglydesigned output changeover switches AUS31, AUS32, . . . each havingthree outputs are also provided in a corresponding manner. A substitutefunctional unit can now be selected instead of any desired functionalunit via data lines which are not illustrated. This circuit arrangementallows operation to be maintained when a total of two functional unitsFE or substitute functional units EFE fail.

More than two substitute functional units can, of course, also beprovided or--depending on the reliability--mixed forms can beimplemented.

FIG. 3 illustrates the principle of a double distributor/combiner. Thiscomprises a first winding W1 having a tap which is connected to a centertap of a second winding W2. A signal which is applied to the connectionpoint K1 is distributed uniformly between the connection points K2 andK3. Two signals which are applied to the connection points K2 and K3 canlikewise be emitted, combined, at the connection point K1. Theattenuation between the connection points K2 and K3 is extremely high.Multiple distributors can be formed from the doubledistributors/combiners. Conventional windings or else striplines may beused, depending on the frequency range required.

The combiner VK1 and the distributor VK2, which have the same circuitapart from the amplifiers, are constructed from thesedistributors/combiners.

FIG. 4 shows a particularly advantageous drive for the pin-diodeswitches. Two diodes D1 and D2 are interconnected by the sameconnections, which form the input of an input changeover switch or theoutput of an output changeover switch. Inputs E, (E1, E2) or outputs A1,A), (A) are DC-decoupled by capacitors C, C1, C2. The diode D1 isforward-biased via the resistor R by means of an operating voltage U1(approximately +3 to +5 V) which is applied via an inductor DR1, whilethe other diode D2 is reverse-biased by a control voltage U2=0 V. If thecontrol voltage U2 is raised to +10 V, then the diode D2 isforward-biased, but the diode D1 is reverse-biased, since approximately+9 V are now present on its cathode. A parallel-path diode, which isconnected to the input E1 (output A1) can at the same time be connectedthrough earth by the control voltage U2. Only one control voltage 0/U2and only one control line are required for this advantageousarrangement.

FIG. 5 shows a pin-diode arrangement which has parallel-path diodes D11and D12. The diodes D1 and D12 are forward-biased by a positive controlvoltage U11, while the diodes D2 and D11 are reverse-biased by a controlvoltage U2.

The control voltage is applied to the series-path diodes D1 and D2 viaresistors R1 and R2. The common junction point is connected to groundvia an inductor R3. This circuit requires only one inductor D3.Inductors can, of course, also be used instead of the resistors R1 andR2 as well as R3 and R4.

FIG. 6 shows the outline circuit diagram of a variant of the passivecombiner. This is constructed using electronic switches SK1, SK2, . . ., to whose inputs E1, E2, . . . the input signals ES1, ES2, . . . aresupplied, one of which is in each case connected through via a singleclosed electronic switch as a substitute input signal EES, via anassociated decoupling resistor RE, to a common junction point andgenerally via an amplifier V1--to the substitute functional unit.

FIG. 7 illustrates the outline circuit diagram of a correspondingdistributor, in which the substitute output signal EAS--generally via anamplifier V2--is connected through from a splitting point, via in eachcase one decoupling resistor RE and, once again, an electronic switchSV1, SV2, . . . , to one of the outputs A1, A2, . . . In contrast to adistributor which is constructed using, for example, doubledistributors/combiners, the substitute output signal is in this caseconnected through to only one output.

FIG. 8 illustrates an advantageous embodiment of the passive combiner,in which in each case two pin-diodes DK1, DK2 are interconnected bytheir same electrodes. Their other connection is in each case routed viaa coupling capacitor C to an input E1, E2, . . . One of the diodes canbe forward-biased via control inputs SE11, SE12, . . . via an inductorDR and a filter capacitor CS. The input signal ES1 which is connectedthrough is then routed from the junction point of the pin-diodes via acommon decoupling resistor REK to the input of the amplifier V1, towhich yet further identically constructed switch pairs are as a ruleconnected.

A corresponding distributor is constructed in FIG. 9. The output of thesecond amplifier V2 is routed via in each case one further decouplingresistor REV to a pin-diode pair, whose identical electrode connectionsare interconnected, while the other diode connections are in each caserouted via coupling capacitors to an output A1, A2, . . . , via whichthe substitute output signal EAS is connected through. In each case onepin-diode is connected through via a filter circuit, comprising aninductor and a filter capacitor, by control voltages which are appliedto control inputs SE21, SE22, . . . .

The invention is not limited to the particular details of the apparatusdepicted and other modifications and applications are contemplated.Certain other changes may be made in the above described apparatuswithout departing from the true spirit and scope of the invention hereininvolved. It is intended, therefore, that the subject matter in theabove depiction shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:
 1. A substitute circuit for a plurality offunctional units processing analog or digital signals, comprising:atleast one combination unit and one substitute functional unit, which isconnected thereto, the at least one combination unit and one substitutefunctional unit being assigned to a plurality of identical functionalunits; at least one electronic input changeover switch, which has aplurality of outputs, assigned to each of said identical functionalunits, via which electronic input changeover switch one input signal foreach of the identical functional units is supplied to a respectiveidentical functional unit of the identical functional unit or to thecombination unit; at least one electronic output changeover switch,which has a plurality of inputs, assigned to each of said identicalfunctional units, via which electronic output changeover switch oneoutput signal from the respective identical functional unit is emittedor a substitute output signal from the substitute functional unit isemitted, via the combination unit; the combination unit having a passivecombiner for combining two input signals, the combination unit havinginputs to which second outputs of the input changeover switches arerouted, and the combination unit having output routed to a signal inputof the substitute functional unit; the combination unit having a passivedistributor for splitting a substitute output signal which comes fromthe substitute functional unit, the passive distributor, having outputsconnected to a respective second input of a respective output changeoverswitch; and all identical functional units connected to a control logicdevice which disconnects a defective identical functional unit based onfault messages via the input changeover switches and the outputchangeover switches and which inserts the substitute functional unit inplace of said defective identical functional unit.
 2. The substitutecircuit as claimed in claim 1, wherein the substitute circuit has atleast two combination units and two substitute functional units, andwherein the input changeover switches have at least three outputs andthe output changeover switches have at least three inputs, and whereinthe outputs and inputs of the changeover switches are connected to thecombination units.
 3. The substitute circuit as claimed in claim 1,wherein the functional units have fault monitoring.
 4. The substitutecircuit as claimed in claim 1, wherein a control logic device isprovided on the combination unit, evaluates the fault messages andcontrols the input and output changeover switches.
 5. The substitutecircuit as claimed in claim 1, wherein the combination unit hasbroadband amplifiers which compensate for attenuation of the combinersand distributors.
 6. The substitute circuit as claimed in claim 1,wherein the identical functional units and changeover switches input andoutput are arranged on an assembly.
 7. The substitute circuit as claimedin claim 1, wherein each of the input changeover switches and outputchangeover switches is a pin-diode changeover switch.
 8. The substitutecircuit as claimed in claim 7, wherein each of the pin-diode changeoverswitches has first and second pin-diodes, and wherein a constant firstcontrol voltage is applied to the first pin-diode, and wherein only asecond control voltage which is applied to the second pin-diode isvaried for switching over.
 9. The substitute circuit as claimed in claim7, wherein each of the pin-diode changeover switches has additionalparallel-path diodes, further control voltages therefore being suppliedvia resistors, and the junction point of a series-path of the first andsecond diodes being connected to ground via an inductor.
 10. Thesubstitute circuit as claimed in claim 1, wherein the passivedistributor and/or the passive combiner is constructed from doubledistributors/combiners or multiple distributors/combiners, respectively,which are constructed using transformers.
 11. The substitute circuit asclaimed in claim 1, wherein the passive combiner is constructed withpin-diode switches which are routed from a plurality of inputs viadecoupling resistors to a junction point and/or the passive distributoris constructed with pin-diode switches which are routed from a commonsplitting point to a plurality of outputs.
 12. The substitute circuit asclaimed in claim 11, wherein for a combiner two pin-diode switches areinterconnected by common connections, which are routed via a commondecoupling element to the junction point, and wherein for a distributor,and wherein each of two pin-diode switches, which are interconnected bycommon connections, are connected via a common decoupling resistor tothe splitting point.